[MRCA] ARC-5/SCR-274-N IF Coil Mod -Continued

[D. Platt]

Gentlemen,

The plot thickens, as they say.  I completed a second set of coils from 
another similar receiver.  The mechanical setup for securing the coil 
bobbins and spacers was different on this one.  Whereas the initial set 
of coils used a long screw up through both coils and terminated at the 
phenolic spacer bar with a nut, this second set has a shorter screw 
coming down through the spacer bar and threaded into the lowermost 
ceramic spacer.  The screw coming from the bottom of the coil assy is a 
short one and threads into the lowermost spacer.  So, the procedure on 
this one was a bit different.

At this point, I'll assume that there are just two setups for securing 
the coil bobbins.  Both types use the same size and spaced ceramic 
spacers.  In this second type, it may be necessary to adjust either of 
the two resonating caps such that the plates do not block access for the 
loosening of the securing screw (from the top). After clearing access to 
the screw, holding the lowermost spacer with a tiny long-nose or 
hemostat, unscrew the securing screw from the spacer.  Then, remove the 
screw securing the spacer from the bottom of the coil assy.

At this point, the lowermost spacer may be carefully jimmied out of the 
coil assy.  Using a soldering iron, heat and slide the wires going to 
the lower coil down a bit to provide some slack.  It may be necessary to 
re-heat and re-solder these wires to ensure continuity.  After providing 
some slack in the wires, its possible to move the lower coil downward to 
provide the necessary increase in spacing.  In my case, I inserted a 
nylon washer between the bottom of the coil assy and the bottom of the 
coil bobbin and added a dollop of epoxy to secure the coil bobbin.  I 
then added some epoxy to the top of this bobbin and to the top and 
bottom of the upper coil bobbin as well as to the top of the securing 
screw.  Before adding epoxy to this screw head, ensure that it, and the 
phenolic spacer bar, are down just far enough to keep clear of the two 
resonating variable capacitors.  When all's well, add a bit of epoxy to 
secure everything.  Also, be sure and check for continuity of each of 
the coils bfore putting everything back together.  So far, thiese mods 
have genuinly helped with selectivity.....

As I mentioned in the first posting of this procedure, after one does 
the first coil set, the procedure is no big deal......  One needs not to 
be a jeweler or surgeon.

Does anyone think a submission to ER, probably with photos, might be 
informative?

Jeep - K3HVG